*sighs*, sorry.
All it took me is to write this question to then figure out I needed to have installed Ruby and the compass gem. Now it makes sense: the process for compiling would not spawn up.
After installing Ruby, run:
gem install compass
And you should be good to go.
EDIT: After you install Ruby, you need to make sure that the ruby runtime files’ path is added to your PATH variable. (Thanks JagWire!)